Possible memory leak with Python 3.9

When frozendict is converted to string in python 3.9, it causes allocations of memory which can not be released with gc.collect()

import gc
import psutil
from frozendict import frozendict

def rss():
    return psutil.Process().memory_info().rss

def process(body):
    str(body)

if __name__ == '__main__':
    initial_memory = rss()
    for i in range(100000):
        payload = frozendict({"text": "Hello", "category": "electronics", "keyword": "electronics"})
        # payload = {"text": "Hello", "category": "electronics", "keyword": "electronics"}
        process(payload)

    print("memory before: ", initial_memory)
    gc.collect()
    print("memory after:  ", rss())

Result with frozendict

memory before:  13094912
memory after:   27693056

Result with builtin dictionary

memory before:  13086720
memory after:   13086720

slezica / python-frozendict

Possible memory leak with Python 3.9 #38